The present invention relates to the manufacture of pipes, and more particularly to apparatus for the manufacturing of continuous lengths of metal pipe from a flat metal strip.
Stationary and mobile pipe forming devices for making a continuous length of metal pipe from flat metal strip material are well known in the prior art. See, for example, descriptions of mobile pipe forming mills in Vassar U.S. Pat. No. 3,014,118, issued Dec. 19, 1961; Sprung et al., U.S. Pat. No. 3,145,758, issued Aug. 25, 1964; Tsuyama, et al., Canadian Pat. No. 1,160,436 issued Jan. 17, 1984; Anderson Canadian Pat. No. 1,119,849, issued Mar. 16, 1982; and Ferreroele, Canadian Pat. No. 627,513, issued Sept. 19, 1961.
Because of their length, size and weight, there have been problems of manoeuvrability and weight in such prior art mobile line pipe mills particularly where a two vehicle apparatus, such as described and illustrated in Vassar U.S. Pat. No. 3,014,118, has been used. Such devices turn and back up often with great difficulty, and have trouble moving over uneven, spongy or muddy terrain such as in tundra or swamp areas.
Another problem arising from the very nature of such mobile pipe mills, is that the frames on which the mills are mounted must withstand torsional twisting while the mill is operating. This may be extremely difficult as the mill moves over rough and uneven terrain, and is further aggravated by the required length of such pipe mills, particularly where they are located on a single vehicle apparatus. If the frame twists as the mobile mill operates, the flat middle metal strap being passed through the mill for forming of metal pipe becomes mis-aligned with respect to the pipe forming and welding elements of the mill, making the continuous operation of the mill virtually impossible.
Prior references of general background interest relating to the motivation, steering and suspension of tracked vehicles are Canadian Pat. No. 748,330 of Nodwell et al, issued Dec. 13, 1966; No. 783,476 of Hand, issued Apr. 23, 1968; No. 793,172 of Messenger, issued Aug. 27, 1968 and No. 1,160,263 of Trask, issued Jan. 10, 1984.
It is an object of the present invention to provide a more manoeuvrable mobile pipe forming apparatus which may be self contained on a single carriage. It is a further object of the present invention to provide an improved suspension for the carriage for such a mobile pipe forming apparatus which enables the apparatus to be carried over uneven terrain with reduced torsional twisting of its carriage.